What is "circumstantial evidence"? What has it got to do with Toms conviction?this is in chapter 23

Actually, circumstantial evidence can be both something you see or hear as well as something you can touch.  For example, if the defendant in a case owns a gun and that gun was used to kill someone, then it is circumstantial evidence.  It infers that the defendant killed the victim but doesn't prove it.

If someone sees the defendant shoot the victim, that is direct evidence.

Usually circumstantial evidence is grouped together to be stronger as one or two pieces of it are usually not sufficient to convict someone.

In Tom's case, all of the evidence is circumstantial but it isn't enough to actually convict him.  It is the prejudice of the community and the desire to convict him rather than to find the truth that allows the use of that circumstantial evidence to form the basis of his conviction.